Field of the Invention
The present invention relates to a technology of reducing magnetic noise caused in ground wiring in a solid-state image pickup element.
Description of the Related Art
In recent years, higher and higher image quality is desired in a solid-state image pickup element. In order to realize high image quality, noise suppression is essential. As such a method of suppressing noise, a technology of suppressing noise caused by a power supply configured to drive the solid-state image pickup element is described in, for example, Japanese Patent Application Laid-Open No. 2008-85994. In the technology described in Japanese Patent Application Laid-Open No. 2008-85994, noise is suppressed through holding, in a hold capacitor, a reference signal of a readout circuit.
In the related art described in Japanese Patent Application Laid-Open No. 2008-85994, noise caused in a signal line of the readout circuit can be suppressed, but noise caused in ground wiring is not taken into consideration. However, when there is a magnetic field, the influence of magnetic noise on the ground wiring cannot be neglected. The reason is that, when the ground wiring, together with a substrate inside or outside the solid-state image pickup element, is in the shape of a loop, induced electromotive force by Faraday's Law is caused in the ground wiring, and appears on a sensor output image as magnetic noise. Therefore, the technology described in Japanese Patent Application Laid-Open No. 2008-85994 has a problem in that magnetic noise caused in the ground wiring cannot be reduced.